A switched-mode power converter (also referred to as a “power converter” or “regulator”) is a power supply or power processing circuit that converts an input voltage waveform into a specified output voltage waveform. Dc-dc power converters convert a direct current (“dc”) input voltage into a dc output voltage. Controllers associated with the power converters manage an operation thereof by controlling conduction periods of power switches employed therein. Some power converters include a controller coupled between an input and output of the power converter in a feedback loop configuration (also referred to as a “control loop” or “closed control loop”) to regulate an output signal or characteristic of the power converter. Typically, the controller measures the output characteristic (e.g., an output voltage, an output current, or a combination of an output voltage and an output current) of the power converter, and based thereon modifies a duty cycle which can be an ON time or a switching frequency of a power switch of the power converter to regulate the output characteristic. Other power converters operate in an open-loop manner wherein an output voltage is produced substantially proportional to an input voltage.
The number of physical input pins on integrated circuits (“ICs”) such as mixed-signal integrated circuits that embody a controller for a power converter typically sense a single analog voltage level entering the integrated circuit, and are limited to adjustment of only one internal signal level by that analog voltage level through external components. Occasionally, there is also a logic function associated with these input pins as well, but only a single voltage level sense. Thus, additional pins are conventionally added to an integrated circuit to provide additional voltage inputs for an internal signal that is utilized by the controller. However, the additional integrated circuit pins are expensive, especially when exceeding a typical package limit (e.g., changing from 16 to 17 or more pins). It is highly advantageous from a manufacturing cost perspective to maintain a standardized pin arrangement.
Accordingly, what is needed in the art is a design approach and related method for a control system for a power converter that enables multiple functional use of an integrated circuit input pin without compromising product performance, and that can be advantageously adapted to high-volume manufacturing techniques without adding significant cost. A further need in the art is elimination of an opto-isolator by sharing an opto-isolator (e.g., a feedback opto-isolator) with another opto-isolator (e.g., a fault opto-isolator) in the power converter.